高強度聚焦超音波(High Intensity Focused Ultrasound, HIFU)為熱治療手術方式之一，相較於傳統手術，其有無輻射、出血量少與非侵入性等優點，目前在前列腺、乳癌、肝臟等腫瘤治療上都有其應用，且對於血腦障壁的開啟及微氣泡藥物釋放等都有功效。HIFU燒灼治療主要的作用機制是以機械效應和熱效應在生物體內產生高溫，使目標處的細胞產生凝固性的壞死，然而HIFU換能器的聚焦點會因元件設計或製造的不夠精準或導引系統的定位誤差而有所偏移，導致在使用時會無法準確聚焦在選定的位置上。本研究藉由機械手臂控制HIFU換能器分別沿三個相互垂直的路徑來回移動並進行燒灼，同時以熱電偶量測燒灼溫度，由所得的兩條溫度-位置曲線的交點找視為HIFU換能器真正的聚焦點位置，並將此校正後的聚焦點位置應用在超音波影像導引HIFU燒灼定位系統。實驗以NIPAM-52水膠做為校正用的仿體，取其可逆的特性使同路徑的來回燒灼條件一致。實驗結果顯示由定位探針點選的熱電偶位置與以機械手臂移動HIFU換能器的燒灼聚焦點位置距離誤差在1 mm 以下。同樣方式的實驗也應用在豬里肌肉的燒灼，結果顯示在2秒內燒灼區可升溫至攝氏80度，達到使細胞壞死的功效。;HIFU(High-Intensity Focused Ultrasound) treatment is a kind of thermal treatment procedures. Comparing to conventional surgical treatment, HIFU treatment has lots of advantages such as radiation-free, less bleeding and noninvasiveness. Currently, HIFU has been applied in tumor treatments such as prostate, breast, and liver tumors. It is also used in the disruption of the blood-brain barrier and microbubble drug delivery. The main mechanisms of HIFU ablation treatment involve mechanical and thermal effect, which can generate high temperature to heat and destroy target cells. However, its position of focal point may not be accurate during ablation positioning because the design or manufacturing of system components are not accurate enough and inaccurate positioning of the robotic HIFU positioning system. In this study, we find the real focal point of a HIFU transducer by moving the HIFU transducer controlled by a robot manipulator to ablate an phantom along three orthogonal paths back and forth. A thermal couple is used to detect ablation temperature at the same time. Then the intersection of the two temperature-position curves obtained during the back and forth movement along the same path is defined as the focus point position of the HIFU transducer, which is used to position the HIFU transducer for an ultrasound assisted robotic positioning system. In the experiment, NIPAM-based hydrogel phantoms are used because of its reusable property of quick recovery from HIFU ablation. The experimental results shown that the distance between the target tip point position of a thermal couple measured by a positioning detector and the ablation focus point of a HIFU transducer controlled by a ultrasound assisted robotic positioning system is less than 1 mm. Similar experimental procedures are applied to ablate pig loin tissue. The temperature of ablation area raises to 80 degrees Celsius in two minutes, which is high enough to destroy tissue cells.
